The present invention relates to a fastening system for providing a stump type swage fastener which is set with a high residual clamping force and for providing a novel tool for setting such fastener.
Stump type swage fasteners and tools for setting the same are generally shown in U.S. Pat. No. 2,396,661 issued to P. B. Keller, et al on Mar. 19, 1946, and 2,764,045 issued to P. C. Koenig on Sept. 25, 1956. With prior tools or devices for setting stump type swage fasteners the contour of the swage surface is such that resultant clamping loads of the set fastener are normally significantly less than would be obtained with a pull type swage fastener, i.e. of a type generally shown in U.S. Pat. No. 2,531,048 issued to L. C. Huck on Nov. 21, 1950. This occurs because the swage surface of the pull type tools has a more desirable contour whereby more metal can be advantageously moved to enhance clamping. (One form of pull gun for a pull type swage fastener and having a multi-pieced anvil with the desired swage surface contour is shown in U.S. Pat. No. 3,329,000 issued to C. J. Schwab on July 4, 1967.) One difficulty with some prior devices for setting the stump type swage fasteners has been in the high forces necessary to effect the swage. Another difficulty with other such devices has been the need for a relatively high force for removing the same from the swaged fastener. In these cases the desired swage surface contour cannot be readily used.
With the system of the present invention a device is utilized having a desired swage surface contour (similar to that of a pull type swage device) for setting stump type swage fasteners whereby a high clamping force is obtained and in which the application and removal loads are minimized. At the same time the provision of a relief angle or radius at the swaging surface of the device minimizes galling of the swaged surfaces on the fastener and results in visible axial lines providing a positive indication that the fastener has been properly set.
It should be understood that the phrase `stump type swage fastener` refers to a two piece fastener including a pin and a sleeve in which the sleeve is swaged onto the pin without a relative pulling force applied between the pin and sleeve; this, of course, is in contrast to the pull type swage fastener previously referred to.